Acyclic olefin isomerization in nitrogen atmosphere using cobalt hydride complexes

ABSTRACT

Cobalt hydride complexes containing tertiary phosphine, arsine or stibine ligands are employed as catalysts for isomerization of olefins. Enhanced catalytic activity is achieved by use of nitrogen in the isomerization.

United States Patent Pennella 51 Sept. 2, 1975 3,721,7l8 3/1973 Hughesct al. 260/6832 Primary Examiner-Veronica O'Keefe [75] inventor: FilippoPennella, Bartlesvilie, Okla. Anomey, Agent or Firm Neuman Williams [73]Assignee: Phillips Petroleum Company, de o & 0 0

Bartlesville, Okla.

[22] Filed: Nov. 19, 1973 [2]] Appl. No.: 416,806 [57] ABSTRACT [52] US.Cl. 260/683,: Cobalt hydride complexes containing tertiary phos- [Sl]Int. Cl. C07c 3/62 phine, arsine or stibine ligands are employed ascata- [58] Field of Search 260/683.2 lysts for isomerization of olefins.Enhanced catalytic activity is achieved by use of nitrogen in theisomeri- [5 References Cited zation.

UNITED STATES PATENTS 3.692.852 9/1972 Tabler 260/6832 7 Claims, 1Drawing Figure I00 TEST uuoen PRETREATIENT o A Arilutrn) none 90 A C Arilutm) Ar FLUSH E] o Ariluim) NZFLUSHJHEN Ar FwsHae-n'o a0 I o N iZotrn)AFTER NzFLUSHat-16'C a Nzflniml uo FLUSH I g E E 40 T I! O I l TIME(MINJ PATtNTED EP I 2 I975 3,903,190

I00 l. TEST UNDER PRETREATMENT t O A Ar(lotm) NONE 90 A C Ar(loim) ArFLUSH E] o Arumm) N FLUSHJHENArFLUSHof-76C so I o N (2orm) AFTER NFLUSHot76C a N (loim) N0 FLUSH 5o LLI 2 DJ 40 f T O l l o 50 I00 I50TIME (MIN) I phosphine] CoH ACYCLIC OLEFIN ISOMERIZATION IN NITROGENATMOSPHERE USING COBALT I-IYDRIDE COMPLEXES This invention relates toolefin double bond isomerization by contacting an olefin with a cobalthydride complex Containing tertiary phosphine, arsine or stibineligands.

Various processes for isomerizing olefins are known in the art. Ingeneral, prior art processes suffer from one or more limitations such asexcessive olefin cracking, undesirable olefin polymerization, excessiverandomization or unfavorable economies. The identification of newcatalyst systems which are effective isomerization catalysts,particularly where the catalyst sys tems can be applied selectively in apredictable manner, is of continuing interest and of potential economicbenefit to the chemical industry at large.

It is an object of this invention to provide a process for the doublebond isomerization of olefins. In addition, it is an object tocatalytically isomerize terminal olefins into internal olefins. Anotherobject is to provide a process for the isomerization of straight-chainterminal olefins to straight-chain internal olefins wherein the internalolefin mixtures contain substantially equal amounts of trans and cisisomers.

Accordingto this invention, the double bond of an isomerizable olefinreactant is shifted by contact with a cobalt hydride complex containingtertiary phosphine, arsine or stibine ligands.

The cobalt hydride complex employed in this invention can be representedby the formula wherein:

Z is independently selected from phosphorus, arsenic or antimony;

Y is selected from H N and N11 and R is independently selected fromhydrocarbyl radicals containing from 1 to carbon atoms including alkyl,aryl, monohalogenated aryl, cycloalkyl radicals and combinations thereofsuch as alkaryl, aralkyl and alkcycloalkyl radicals. Examplesinclude:(triphenylphosphine) Col-I (triethylp hosphine Col-I( N 2(4-methy1phenyl) phosphine -CoH( NI-l (phenyldimethylphosphine CoH(N(diphenylmethylphosphine) Col-l (dimethyllaurylarsine) CoI-I(Nl-l(trimethylarsine) Col-I (tribenzylarsine CoH N (tricyclohexylarsine.CoH( NH (trieicosylarsine Col-I(N (Triphenylstibine CoI-I(4methylcyclohexyl) phosphine1 CoH( N (tridecylstibine CoI-I( NH[(4-fluorophenyl phosphine -CoI-I( N [(4-chlorophenyl(triisobutylstibine) CoI-I(NI-I (triphenylphosphineh- (triphenylarsine)CoH( N triphenylphosphine Col-I(N and the like and combinationsthereof.

The cobalt hydride complexes of this invention can be prepared by anyconvenient method known in the art. Generally convenient methods areillustrated in J. Orgqnqmetal. Chem. 16 (1969), pages l4, J.Organometal. Chem. 19 (1969), pages'24l-244 and Inorg. Syn, Vol. xii,pages 12-22.

Examples of convenient methods are treating a chilled mixture of cobaltII or III acetylacetonate and a trialkylor triarylphosphine dissolved inan organic solvent under a hydrogen atmosphere with a reducing agentsuch as di-n-butylaluminum hydride and isolating the product. Thenitrogen complex is formed by dissolving the product in a solvent suchas diethyl ether and bubbling nitrogen through the mixture. The complexis recovered after evaporating the solvent.

In another process, the nitrogen complex is formed directly by treatinga mixture of the cobalt acetylacetonate and trialkylor triarylphosphinein an organic solvent at room temperature in a nitrogen atmosphere withtriisobutylaluminum and isolating the product.

The cobalt dinitrogen and ammonia complexes can be prepared convenientlyby the addition of nitrogen or ammonia directly to a (R Z) Col-icomplex.

The cobalt complexes employed in this invention are air-sensitive andare generally unstable in the presence of air or oxygen-containingatmospheres. Accordingly, the preparation and use thereof should excludeor appreciably restrict air or oxygen, as well as exclude any reactivesubstance or atmospheres which tend to re duce the effectiveness of thecomplex in an isomerization process. Thus, in carrying out anisomerization with the catalysts, an atmosphere such as argon, helium,neon, krypton, nitrogen, etc. or combinations thereof is maintained overthe reaction mixture. Pressures ranging from 0.1 atmosphere toatmospheres are operable, more preferably 1lO atmospheres.

In accordance with one preferred embodiment of the invention, nitrogenis employed in the"'atrnosphere maintained over the reaction mixture,itihavin'g been found that nitrogen dramatically enhan cesactivity ofthe catalysts. Also, isomerization in the presence of 'nitrogen resultsin the product mixture containing approximately 50% of each of cis andtrans isomers.

In general, the cobalt complexes have limited solubility in commerciallyimportant olefin isomerization and hydrogenation process feedstocks.Advantageously, in some cases, therefore, the complex is employed in thepresence of substantially inert solvents to facilitate mixing of olefinreactant and cobalt catalyst. Representative inert organic solventswhich can be used include aromatic hydrocarbons including benzene,toluene, ortho-xylene, meta-xylene, para-xylene, as well as other inertsolvents including tetrahydrofuran and similar solvents.

The cobalt complexes can be employed in catalytic olefin isomerizationreactions by depositing the complex on a solid inorganic oxide catalystsupport. Such support materials are commonly known as refractory oxidesand include synthetic materials as well as acid treated clays or thecrystalline aluminosilicates known in the art as molecular sieves.Generally, about 1 to 10 weight percent complex based on theiweight ofthe support is preferred. Suitable supports include silica, alumina,silicaalumina, titania, thoria, zirconia, etc. and combinations thereof.The support is preferably calcined at an elevated temperature, i.e.about 425 to about 650 C. in air and cooled in nitrogen, hydrogen, etc.before admixing with the complex. lmpregnation of the support with asolution or slurry of the complex followed by removal of the solvent isthe preferred method of. preparation, although any conventional methodcan be employed, such as dry mixing.

Suitable starting materials are isomerizable olefins including acyclicmonoenes and acyclic polyenes encompassing conjugated and non-conjugateddienes, trienes, mixtures thereof and the like. The olefins can containaryl or cycloalkyl substituents or combinations thereof. Preferredolefins, because of their commercial importance, contain from 4 to 20carbon atoms per molecule and more preferably from 4 to carbon atoms permolecule. Examples of the olefins include: l-butene, l-pentene,l-hexene, 3-hexene, l-decene, S-methyl- 1 -hexene, 7-methyll -nonene,S-ethyll octene, 2-butene, 2-pentene, 4-methyl-2-hexene, 4- phenyll-butene, S-cyclopentyll -pentene, 4-phenyl-2- butene,S-isopropyl-Z-heptene Z-decene; 2,3 ,4-trimethyl-6-dodecene; l,3-tetradecadiene, 4- eicosene', l-( 3-butenyl )-4-ethylbenzene; l-( 3-EXAMPLE 1 0.22 gram of (triphenylphosphinehCol-KN was dissolved in 40milliliters of toluene under an argon atmosphere in a glove box. Thesolution was divided into equal parts, each part was placed in amilliliter Diels-Alder tube and the tubes were sealed with neoprenecaps. One tube A was placed in a bath held at 25 C. and 2 milliliters(about 1.3 grams) of l-pentene was added to the solution with vigorousstirring. A stream of nitrogen was passed through the solution in theother tube B for 2 hours while the solution was being stirred. That tubewas left overnight in the dark under l4 psig nitrogen. The tube was thenplaced in a bath held at 25 C. and 2 milliliters of l-pentene were addedto the solution with vigorous stirring. Periodically, l0 microlitersamples were removed from each tube and analyzed by gas-liquidchromatography. The following results were obtained:

Table 1 Tube A (Under Argon) Tube B (Under Nitrogen) Mole Mole k TimeTrans-2 cis-2 Trans-2 Cis-2 (min. l-Pcntene Pentcne Pentcnc l-PentenePentenc Pentcnc O l ()0 0 O l()() O 0 L5 86 8 (i 87 6 6 7 77 9 I I4 70l3 17 22 60 l l 29 42 25 33 38 49 I2 39 26 32 42 S4 l4 46 l7 36 48 70 3316 5l 1']. 39 49 90 28 I I6 56 8 4l Si 106 6 43 5O l07 23 18 5X I26 20I9 6i 5 50 150 16 20 63 4.2 45 50 181 l3 22 65 Hi3 3.8 47 48 20 parts byweight of complex per 100 parts by weight of olefin are suitable to thepractice of this invention.

The isomerization processes can be carried out as either a batch or as acontinuous process using any conventional apparatus. Depending on themode of reaction and other conditions such as reaction temperature andcomplex: olefin weight ratio, contact time can vary from 1 minute to 100hours, at any convenient pressure, ranging from subatmospheric to about2000 psig and more preferably from about 0 to 2000 psig.

The reaction products of this invention can be separated from thereaction mixtures by any method known in the art. Suitable separationtechniques include filtration, distillation, decantation, adsorption andthe like.

The following examples are given to illustrate the processes of thisinvention and are not intended to unduly limit the scope of the presentinvention in strict accordance therewith.

In both cases 0.5 mole percent pentane is also formed. The above datashow that isomerization proceeds more rapidly under a nitrogenatmosphere than under an argon atmosphere. For example, in Tube B, 84%conversion is obtained in 54 minutes whereas in Tube A, it requires 150minutes to obtain 83% conversion. The. data also show that apredominantly cis isomer is obtained after about 90 minutes or longerwhen an argon atmosphere is used whereas in a nitrogen atmosphere thecis and trans isomers are present in more equal amounts.

EXAMPLE II 0.4 gram of (triphenylphosphine) Col-lN was dissolved inmilliliters of toluene in a glove box under argon free of oxygen ormoisture. The solution was divided into four equal parts. Each 20milliliter portion was placed in a DielsAlder tube equipped with amagnetic stirrer. The tubes were sealed with neoprene seals and removedfrom the glove box.

The isomerization tests were carried out at 25 C. i 0.2 at atmosphericpressure unless otherwise specified. 2 milliliters of pentene-l wereadded to each tube as indicated below. 10 microliters were removed atregular intervals and analyzed by gas-liquid chromatography on a 20 footbio-ether column.

Tube A The pentene was added without any pretreatment.

Tube B The solution was flushed with N for 1 hour and the pentene wasadded to the solution under 1 atm. of N Tube C The solution was flushedwith argon for 1 hour and the pentene was added to the solution under 1atm. of argon.

Tube D The solution was flushed with N for 80 minutes to bring about thesame changes that might occur in Test B. The solution was then cooled to76 C. and the nitrogen purged from the system by flushing with argon for90 minutes. The temperature was raised to 25 C., the pentene was addedto the solution under 1 atm. of argon and the reaction was allowed toproceed.

Tube D, Part 2 After the reaction had proceeded for 80 minutes thesolution was cooled to -76 C. to stop the reaction and was flushed withN for 20 minutes. It was then charged with two atmospheres of N andbrought back to 25 C. and the reaction allowed to proceed.

The results of these tests are summarized in FIG. 1 from which it isclear that the reaction proceeds at the same rate in an argon atmosphereregardless of the pretreatment of the solution (tests A, C and D), andthat the reaction proceeds much more rapidly under N The half times, t/2, i.e., the times needed for half of the pentene-l to be isomerized(obtained from FIG. 1) are 27.5 minutes under 1 atmosphere of N and 53.5minutes under 1 atmosphere of Ar. Thus, the reaction rate is almostexactly twice as fast under N than under Ar.

Comparison of the results obtained in Test B under 1 atmosphere of Nwith those obtained in Test D (part 2) under 2 atmospheres of N showsthat the reaction is further increased by increasing the pressure(concentration) of N Thus, to reduce the pentene-1 concentration from39.5 to 93 minutes are needed under 1 atmosphere of N and only 65minutes under 2 atmospheres.

Those modifications and equivalents which fall within the spirit of theinvention are to be considered a part thereof.

What is claimed is:

1. An isomerization process which comprises contacting under suitableisomerization conditions and in the presence of molecular nitrogen anacyclic olefin reactant with a cobalt hydride complex represented by theformula wherein Z is independently selected from phosphorus, arsenic orantimony;

Y is selected from H N and NH and R is independently selected fromhydrocarbyl radicals containing from 1 to 20 carbon atoms includingalkyl, aryl, monohalogenated aryl, cycloalkyl radicals and combinationsthereof, and recovering substantially equal amounts of cis and transolefin isomers.

2. A process in accordance with claim 1 wherein the contacting iscarried out under pressure within the range of about 0 to about 2000psig and a temperature within the range of about -20 C. to about C. andsaid contacting period is in the range of about 1 minute to about hours.

3. A process in accordance with claim 1 wherein the contacting iscarried out over a heterogeneous catalyst of said cobalt hydride complexsupported on a solid in organic oxide.

4. A process in accordance with claim 1 wherein Y is nitrogen.

5. A process in accordance with claim 1 wherein Y is hydrogen.

6. A process in accordance with claim 1 wherein Y is ammonia.

7. A process in accordance with claim 1 wherein said R is alkyl,cycloalkyl, aryl hydrocarbyl radicals or com-

1. AN ISOMERIZATION PROCESS WHICH COMPRISES CONTACTING UNDER SUITABLEISOMERIZATION CONDITIONS AND IN THE PRESENCE OF MOLECULAR NITROGEN ANACYCLIC OLEFIN REACTANT WITH A COBALT HYDRIDE COMPLEX REPRESENTED BY THEFORMULA
 2. A process in accordance with claim 1 wherein the contactingis carried out under pressure within the range of about 0 to about 2000psig and a temperature within the range of about -20* C. to about 70* C.and said contacting period is in the range of about 1 minute to about100 hours.
 3. A process in accordance with claim 1 wherein thecontacting is carried out over a heterogeneous catalyst of said cobalthydride complex supported on a solid inorganic oxide.
 4. A process inaccordance with claim 1 wherein Y is nitrogen.
 5. A process inaccordance with claim 1 wherein Y is hydrogen.
 6. A process inaccordance with claim 1 wherein Y is ammonia.
 7. A process in accordancewith claim 1 wherein said R is alkyl, cycloalkyl, aryl hydrocarbylradicals or combinations thereof.